Japan protested to North Korea on Friday over the launch of what Tokyo has identified as ballistic missiles, government officials said, amid renewed tensions over its arms development program.

"The ballistic missile launch clearly violates relevant U.N. Security Council resolutions and is extremely regrettable," Deputy Chief Cabinet Secretary Kotaro Nogami said at a press conference. The protest was lodged through the Japanese Embassy in Beijing.

The government scrambled to determine what was behind North Korea's second launch of missiles in a week on Thursday, in close coordination with the United States and South Korea.

Hours after the U.S. Defense Department said the projectiles were ballistic missiles, Japanese Defense Minister Takeshi Iwaya gave the same assessment.

"Based on our comprehensive analysis of the information, the government believes the projectiles launched by North Korea on Thursday were short-range ballistic missiles," Iwaya told reporters.

Still, Japanese officials said that for now the latest tests will not impede Tokyo's efforts to explore holding a summit "without conditions" between Prime Minister Shinzo Abe and North Korean leader Kim Jong Un.

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"North Korea is trying to drive a wedge between Japan, the United States and South Korea. There is no doubt about it," a senior Japanese diplomat said.

The diplomat said Japan will wait to see how the Security Council responds as North Korea is prohibited from carrying out ballistic missile tests under U.N. resolutions.

North Korea fired two short-range missiles eastward from the northeastern region of Kusong around 4:30 p.m. on Thursday, according to South Korea's Joint Chiefs of Staff.

U.S. President Donald Trump, who has met with Kim twice, said "Nobody's happy" about the latest development, which analysts see as a sign of Pyongyang's mounting frustration with Washington.

Diplomatic sources have said that the projectiles North Korea fired last Saturday also included a ballistic missile but Washington has withheld the assessment from the public for fear of hampering U.S.-North Korea denuclearization talks, which have stalled since Trump's second summit with Kim in late February broke up without an agreement.

Abe, for his part, has stated his resolve to realize his first meeting with Kim "without conditions," a shift from his previous stance that a guarantee of progress on the long-standing issue of Japanese nationals abducted by North Korea in the 1970s and 1980s is a prerequisite for any summit.

"The prime minister has a very strong determination to act boldly without missing any opportunity available and resolve the issue," Deputy Chief Cabinet Secretary Yasutoshi Nishimura said at a separate press conference earlier Friday. "It's an issue that Japan needs to tackle proactively."